Meeting the requirements of specification O.30/35, the Blackburn Roc was essentially a fighter variant of the Blackburn Skua shipboard dive-bomber. The design and construction of the two aircraft were fundamentally the same, with the Roc differing from its stablemate in having a slightly wider fuselage (to accommodate a Boulton-Paul "A" power-driven turret equipped with four 0.303-in Browning machine guns), and with an increased wing dihedral. A contract for 136 aircraft was placed on April 28, 1937 with manufacture sub-contracted to the Boulton-Paul Company. The first three production machines (L3057-3059) served as the prototypes, with the first of these making its maiden flight on December 23, 1938. The third aircraft (L3059) being experimentally fitted with twin floats to specification 20/37, being completed in this form in December 1939. The weight and drag of the turret was soon found to seriously impair performance. Attempts to rectify this by fitting a larger propeller and various other means all proved unsuccessful. After a brief period in front-line service the Rocs were soon relegated to second-line duties. Like its Royal Air Force counterpart, the Boulton-Paul Defiant, the concept of a two-seat single-engined turret fighter proved to be faulty. The idea of bringing a quartet of machine guns to bear on enemy bombers proving to be tactically unsound. Bibliography Warplanes of the Second World War-Fighters Volume 2 (William Green, MacDonald,1961) World Aircraft Information Files (Aerospace Publishing Periodical).